4.1 Exponential Functions

g ( x ) = 0.875 x g ( x ) = 0.875 x and j ( x ) = 1095.6 βˆ’ 2 x j ( x ) = 1095.6 βˆ’ 2 x represent exponential functions.

5.5556 5.5556

About 1.548 1.548 billion people; by the year 2031, India’s population will exceed China’s by about 0.001 billion, or 1 million people.

( 0 , 129 ) ( 0 , 129 ) and ( 2 , 236 ) ; N ( t ) = 129 ( 1 .3526 ) t ( 2 , 236 ) ; N ( t ) = 129 ( 1 .3526 ) t

f ( x ) = 2 ( 1.5 ) x f ( x ) = 2 ( 1.5 ) x

f ( x ) = 2 ( 2 ) x . f ( x ) = 2 ( 2 ) x . Answers may vary due to round-off error. The answer should be very close to 1.4142 ( 1.4142 ) x . 1.4142 ( 1.4142 ) x .

y β‰ˆ 12 β‹… 1.85 x y β‰ˆ 12 β‹… 1.85 x

about $3,644,675.88

e βˆ’ 0.5 β‰ˆ 0.60653 e βˆ’ 0.5 β‰ˆ 0.60653

$3,659,823.44

3.77E-26 (This is calculator notation for the number written as 3.77 Γ— 10 βˆ’ 26 3.77 Γ— 10 βˆ’ 26 in scientific notation. While the output of an exponential function is never zero, this number is so close to zero that for all practical purposes we can accept zero as the answer.)

4.2 Graphs of Exponential Functions

The domain is ( βˆ’ ∞ , ∞ ) ; ( βˆ’ ∞ , ∞ ) ; the range is ( 0 , ∞ ) ; ( 0 , ∞ ) ; the horizontal asymptote is y = 0. y = 0.

The domain is ( βˆ’ ∞ , ∞ ) ; ( βˆ’ ∞ , ∞ ) ; the range is ( 3 , ∞ ) ; ( 3 , ∞ ) ; the horizontal asymptote is y = 3. y = 3.

x β‰ˆ βˆ’ 1.608 x β‰ˆ βˆ’ 1.608

f ( x ) = βˆ’ 1 3 e x βˆ’ 2 ; f ( x ) = βˆ’ 1 3 e x βˆ’ 2 ; the domain is ( βˆ’ ∞ , ∞ ) ; ( βˆ’ ∞ , ∞ ) ; the range is ( βˆ’ ∞ , βˆ’2 ) ; ( βˆ’ ∞ , βˆ’2 ) ; the horizontal asymptote is y = βˆ’2. y = βˆ’2.

4.3 Logarithmic Functions

  • ⓐ log 10 ( 1 , 000 , 000 ) = 6 log 10 ( 1 , 000 , 000 ) = 6 is equivalent to 10 6 = 1 , 000 , 000 10 6 = 1 , 000 , 000
  • β“‘ log 5 ( 25 ) = 2 log 5 ( 25 ) = 2 is equivalent to 5 2 = 25 5 2 = 25
  • ⓐ 3 2 = 9 3 2 = 9 is equivalent to log 3 ( 9 ) = 2 log 3 ( 9 ) = 2
  • β“‘ 5 3 = 125 5 3 = 125 is equivalent to log 5 ( 125 ) = 3 log 5 ( 125 ) = 3
  • β“’ 2 βˆ’ 1 = 1 2 2 βˆ’ 1 = 1 2 is equivalent to log 2 ( 1 2 ) = βˆ’ 1 log 2 ( 1 2 ) = βˆ’ 1

log 121 ( 11 ) = 1 2 log 121 ( 11 ) = 1 2 (recalling that 121 = ( 121 ) 1 2 = 11 121 = ( 121 ) 1 2 = 11 )

log 2 ( 1 32 ) = βˆ’ 5 log 2 ( 1 32 ) = βˆ’ 5

log ( 1 , 000 , 000 ) = 6 log ( 1 , 000 , 000 ) = 6

log ( 123 ) β‰ˆ 2.0899 log ( 123 ) β‰ˆ 2.0899

The difference in magnitudes was about 3.929. 3.929.

It is not possible to take the logarithm of a negative number in the set of real numbers.

4.4 Graphs of Logarithmic Functions

( 2 , ∞ ) ( 2 , ∞ )

( 5 , ∞ ) ( 5 , ∞ )

The domain is ( 0 , ∞ ) , ( 0 , ∞ ) , the range is ( βˆ’ ∞ , ∞ ) , ( βˆ’ ∞ , ∞ ) , and the vertical asymptote is x = 0. x = 0.

The domain is ( βˆ’ 4 , ∞ ) , ( βˆ’ 4 , ∞ ) , the range ( βˆ’ ∞ , ∞ ) , ( βˆ’ ∞ , ∞ ) , and the asymptote x = – 4. x = – 4.

The domain is ( 2 , ∞ ) , ( 2 , ∞ ) , the range is ( βˆ’ ∞ , ∞ ) , ( βˆ’ ∞ , ∞ ) , and the vertical asymptote is x = 2. x = 2.

The domain is ( βˆ’ ∞ , 0 ) , ( βˆ’ ∞ , 0 ) , the range is ( βˆ’ ∞ , ∞ ) , ( βˆ’ ∞ , ∞ ) , and the vertical asymptote is x = 0. x = 0.

x β‰ˆ 3.049 x β‰ˆ 3.049

x = 1 x = 1

f ( x ) = 2 ln ( x + 3 ) βˆ’ 1 f ( x ) = 2 ln ( x + 3 ) βˆ’ 1

4.5 Logarithmic Properties

log b 2 + log b 2 + log b 2 + log b k = 3 log b 2 + log b k log b 2 + log b 2 + log b 2 + log b k = 3 log b 2 + log b k

log 3 ( x + 3 ) βˆ’ log 3 ( x βˆ’ 1 ) βˆ’ log 3 ( x βˆ’ 2 ) log 3 ( x + 3 ) βˆ’ log 3 ( x βˆ’ 1 ) βˆ’ log 3 ( x βˆ’ 2 )

2 ln x 2 ln x

βˆ’ 2 ln ( x ) βˆ’ 2 ln ( x )

log 3 16 log 3 16

2 log x + 3 log y βˆ’ 4 log z 2 log x + 3 log y βˆ’ 4 log z

2 3 ln x 2 3 ln x

1 2 ln ( x βˆ’ 1 ) + ln ( 2 x + 1 ) βˆ’ ln ( x + 3 ) βˆ’ ln ( x βˆ’ 3 ) 1 2 ln ( x βˆ’ 1 ) + ln ( 2 x + 1 ) βˆ’ ln ( x + 3 ) βˆ’ ln ( x βˆ’ 3 )

log ( 3 β‹… 5 4 β‹… 6 ) ; log ( 3 β‹… 5 4 β‹… 6 ) ; can also be written log ( 5 8 ) log ( 5 8 ) by reducing the fraction to lowest terms.

log ( 5 ( x βˆ’ 1 ) 3 x ( 7 x βˆ’ 1 ) ) log ( 5 ( x βˆ’ 1 ) 3 x ( 7 x βˆ’ 1 ) )

log x 12 ( x + 5 ) 4 ( 2 x + 3 ) 4 ; log x 12 ( x + 5 ) 4 ( 2 x + 3 ) 4 ; this answer could also be written log ( x 3 ( x + 5 ) ( 2 x + 3 ) ) 4 . log ( x 3 ( x + 5 ) ( 2 x + 3 ) ) 4 .

The pH increases by about 0.301.

ln 8 ln 0.5 ln 8 ln 0.5

ln 100 ln 5 β‰ˆ 4.6051 1.6094 = 2.861 ln 100 ln 5 β‰ˆ 4.6051 1.6094 = 2.861

4.6 Exponential and Logarithmic Equations

x = βˆ’ 2 x = βˆ’ 2

x = βˆ’ 1 x = βˆ’ 1

x = 1 2 x = 1 2

The equation has no solution.

x = ln 3 ln ( 2 3 ) x = ln 3 ln ( 2 3 )

t = 2 ln ( 11 3 ) t = 2 ln ( 11 3 ) or ln ( 11 3 ) 2 ln ( 11 3 ) 2

t = ln ( 1 2 ) = βˆ’ 1 2 ln ( 2 ) t = ln ( 1 2 ) = βˆ’ 1 2 ln ( 2 )

x = ln 2 x = ln 2

x = e 4 x = e 4

x = e 5 βˆ’ 1 x = e 5 βˆ’ 1

x β‰ˆ 9.97 x β‰ˆ 9.97

x = 1 x = 1 or x = βˆ’ 1 x = βˆ’ 1

t = 703 , 800 , 000 Γ— ln ( 0.8 ) ln ( 0.5 ) years  β‰ˆ 226 , 572 , 993 years . t = 703 , 800 , 000 Γ— ln ( 0.8 ) ln ( 0.5 ) years  β‰ˆ 226 , 572 , 993 years .

4.7 Exponential and Logarithmic Models

f ( t ) = A 0 e βˆ’ 0.0000000087 t f ( t ) = A 0 e βˆ’ 0.0000000087 t

less than 230 years, 229.3157 to be exact

f ( t ) = A 0 e ln 2 3 t f ( t ) = A 0 e ln 2 3 t

6.026 hours

895 cases on day 15

Exponential. y = 2 e 0.5 x . y = 2 e 0.5 x .

y = 3 e ( ln 0.5 ) x y = 3 e ( ln 0.5 ) x

4.8 Fitting Exponential Models to Data

  • ⓐ The exponential regression model that fits these data is y = 522.88585984 ( 1.19645256 ) x . y = 522.88585984 ( 1.19645256 ) x .
  • β“‘ If spending continues at this rate, the graduate’s credit card debt will be $4,499.38 after one year.
  • ⓐ The logarithmic regression model that fits these data is y = 141.91242949 + 10.45366573 ln ( x ) y = 141.91242949 + 10.45366573 ln ( x )
  • β“‘ If sales continue at this rate, about 171,000 games will be sold in the year 2015.
  • ⓐ The logistic regression model that fits these data is y = 25.65665979 1 + 6.113686306 e βˆ’ 0.3852149008 x . y = 25.65665979 1 + 6.113686306 e βˆ’ 0.3852149008 x .
  • β“‘ If the population continues to grow at this rate, there will be about 25,634   25,634   seals in 2020.
  • β“’ To the nearest whole number, the carrying capacity is 25,657.

4.1 Section Exercises

Linear functions have a constant rate of change. Exponential functions increase based on a percent of the original.

When interest is compounded, the percentage of interest earned to principal ends up being greater than the annual percentage rate for the investment account. Thus, the annual percentage rate does not necessarily correspond to the real interest earned, which is the very definition of nominal .

exponential; the population decreases by a proportional rate. .

not exponential; the charge decreases by a constant amount each visit, so the statement represents a linear function. .

The forest represented by the function B ( t ) = 82 ( 1.029 ) t . B ( t ) = 82 ( 1.029 ) t .

After t = 20 t = 20 years, forest A will have 43 43 more trees than forest B.

Answers will vary. Sample response: For a number of years, the population of forest A will increasingly exceed forest B, but because forest B actually grows at a faster rate, the population will eventually become larger than forest A and will remain that way as long as the population growth models hold. Some factors that might influence the long-term validity of the exponential growth model are drought, an epidemic that culls the population, and other environmental and biological factors.

exponential growth; The growth factor, 1.06 , 1.06 , is greater than 1. 1.

exponential decay; The decay factor, 0.97 , 0.97 , is between 0 0 and 1. 1.

f ( x ) = 2000 ( 0.1 ) x f ( x ) = 2000 ( 0.1 ) x

f ( x ) = ( 1 6 ) βˆ’ 3 5 ( 1 6 ) x 5 β‰ˆ 2.93 ( 0.699 ) x f ( x ) = ( 1 6 ) βˆ’ 3 5 ( 1 6 ) x 5 β‰ˆ 2.93 ( 0.699 ) x

$ 10 , 250 $ 10 , 250

$ 13 , 268.58 $ 13 , 268.58

P = A ( t ) β‹… ( 1 + r n ) βˆ’ n t P = A ( t ) β‹… ( 1 + r n ) βˆ’ n t

$ 4,572.56 $ 4,572.56

continuous growth; the growth rate is greater than 0. 0.

continuous decay; the growth rate is less than 0. 0.

$ 669.42 $ 669.42

f ( βˆ’ 1 ) = βˆ’ 4 f ( βˆ’ 1 ) = βˆ’ 4

f ( βˆ’ 1 ) β‰ˆ βˆ’ 0.2707 f ( βˆ’ 1 ) β‰ˆ βˆ’ 0.2707

f ( 3 ) β‰ˆ 483.8146 f ( 3 ) β‰ˆ 483.8146

y = 3 β‹… 5 x y = 3 β‹… 5 x

y β‰ˆ 18 β‹… 1.025 x y β‰ˆ 18 β‹… 1.025 x

y β‰ˆ 0.2 β‹… 1.95 x y β‰ˆ 0.2 β‹… 1.95 x

APY = A ( t ) βˆ’ a a = a ( 1 + r 365 ) 365 ( 1 ) βˆ’ a a = a [ ( 1 + r 365 ) 365 βˆ’ 1 ] a = ( 1 + r 365 ) 365 βˆ’ 1 ; APY = A ( t ) βˆ’ a a = a ( 1 + r 365 ) 365 ( 1 ) βˆ’ a a = a [ ( 1 + r 365 ) 365 βˆ’ 1 ] a = ( 1 + r 365 ) 365 βˆ’ 1 ; I ( n ) = ( 1 + r n ) n βˆ’ 1 I ( n ) = ( 1 + r n ) n βˆ’ 1

Let f f be the exponential decay function f ( x ) = a β‹… ( 1 b ) x f ( x ) = a β‹… ( 1 b ) x such that b > 1. b > 1. Then for some number n > 0 , n > 0 , f ( x ) = a β‹… ( 1 b ) x = a ( b βˆ’ 1 ) x = a ( ( e n ) βˆ’ 1 ) x = a ( e βˆ’ n ) x = a ( e ) βˆ’ n x . f ( x ) = a β‹… ( 1 b ) x = a ( b βˆ’ 1 ) x = a ( ( e n ) βˆ’ 1 ) x = a ( e βˆ’ n ) x = a ( e ) βˆ’ n x .

47 , 622 47 , 622 fox

1.39 % ; 1.39 % ; $ 155 , 368.09 $ 155 , 368.09

$ 35 , 838.76 $ 35 , 838.76

$ 82 , 247.78 ; $ 82 , 247.78 ; $ 449.75 $ 449.75

4.2 Section Exercises

An asymptote is a line that the graph of a function approaches, as x x either increases or decreases without bound. The horizontal asymptote of an exponential function tells us the limit of the function’s values as the independent variable gets either extremely large or extremely small.

g ( x ) = 4 ( 3 ) βˆ’ x ; g ( x ) = 4 ( 3 ) βˆ’ x ; y -intercept: ( 0 , 4 ) ; ( 0 , 4 ) ; Domain: all real numbers; Range: all real numbers greater than 0. 0.

g ( x ) = βˆ’ 10 x + 7 ; g ( x ) = βˆ’ 10 x + 7 ; y -intercept: ( 0 , 6 ) ; ( 0 , 6 ) ; Domain: all real numbers; Range: all real numbers less than 7. 7.

g ( x ) = 2 ( 1 4 ) x ; g ( x ) = 2 ( 1 4 ) x ; y -intercept: ( 0 , 2 ) ; ( 0 , 2 ) ; Domain: all real numbers; Range: all real numbers greater than 0. 0.

y -intercept: ( 0 , βˆ’ 2 ) ( 0 , βˆ’ 2 )

Horizontal asymptote: h ( x ) = 3 ; h ( x ) = 3 ; Domain: all real numbers; Range: all real numbers strictly greater than 3. 3.

As x β†’ ∞ x β†’ ∞ , f ( x ) β†’ βˆ’ ∞ f ( x ) β†’ βˆ’ ∞ ; As x β†’ βˆ’ ∞ x β†’ βˆ’ ∞ , f ( x ) β†’ βˆ’ 1 f ( x ) β†’ βˆ’ 1

As x β†’ ∞ x β†’ ∞ , f ( x ) β†’ 2 f ( x ) β†’ 2 ; As x β†’ βˆ’ ∞ x β†’ βˆ’ ∞ , f ( x ) β†’ ∞ f ( x ) β†’ ∞

f ( x ) = 4 x βˆ’ 3 f ( x ) = 4 x βˆ’ 3

f ( x ) = 4 x βˆ’ 5 f ( x ) = 4 x βˆ’ 5

f ( x ) = 4 βˆ’ x f ( x ) = 4 βˆ’ x

y = βˆ’ 2 x + 3 y = βˆ’ 2 x + 3

y = βˆ’ 2 ( 3 ) x + 7 y = βˆ’ 2 ( 3 ) x + 7

g ( 6 ) = 800 + 1 3 β‰ˆ 800.3333 g ( 6 ) = 800 + 1 3 β‰ˆ 800.3333

h ( βˆ’ 7 ) = βˆ’ 58 h ( βˆ’ 7 ) = βˆ’ 58

x β‰ˆ βˆ’ 2.953 x β‰ˆ βˆ’ 2.953

x β‰ˆ βˆ’ 0.222 x β‰ˆ βˆ’ 0.222

The graph of G ( x ) = ( 1 b ) x G ( x ) = ( 1 b ) x is the refelction about the y -axis of the graph of F ( x ) = b x ; F ( x ) = b x ; For any real number b > 0 b > 0 and function f ( x ) = b x , f ( x ) = b x , the graph of ( 1 b ) x ( 1 b ) x is the the reflection about the y -axis, F ( βˆ’ x ) . F ( βˆ’ x ) .

The graphs of g ( x ) g ( x ) and h ( x ) h ( x ) are the same and are a horizontal shift to the right of the graph of f ( x ) ; f ( x ) ; For any real number n , real number b > 0 , b > 0 , and function f ( x ) = b x , f ( x ) = b x , the graph of ( 1 b n ) b x ( 1 b n ) b x is the horizontal shift f ( x βˆ’ n ) . f ( x βˆ’ n ) .

4.3 Section Exercises

A logarithm is an exponent. Specifically, it is the exponent to which a base b b is raised to produce a given value. In the expressions given, the base b b has the same value. The exponent, y , y , in the expression b y b y can also be written as the logarithm, log b x , log b x , and the value of x x is the result of raising b b to the power of y . y .

Since the equation of a logarithm is equivalent to an exponential equation, the logarithm can be converted to the exponential equation b y = x , b y = x , and then properties of exponents can be applied to solve for x . x .

The natural logarithm is a special case of the logarithm with base b b in that the natural log always has base e . e . Rather than notating the natural logarithm as log e ( x ) , log e ( x ) , the notation used is ln ( x ) . ln ( x ) .

a c = b a c = b

x y = 64 x y = 64

15 b = a 15 b = a

13 a = 142 13 a = 142

e n = w e n = w

log c ( k ) = d log c ( k ) = d

log 19 y = x log 19 y = x

log n ( 103 ) = 4 log n ( 103 ) = 4

log y ( 39 100 ) = x log y ( 39 100 ) = x

ln ( h ) = k ln ( h ) = k

x = 2 βˆ’ 3 = 1 8 x = 2 βˆ’ 3 = 1 8

x = 3 3 = 27 x = 3 3 = 27

x = 9 1 2 = 3 x = 9 1 2 = 3

x = 6 βˆ’ 3 = 1 216 x = 6 βˆ’ 3 = 1 216

x = e 2 x = e 2

14.125 14.125

2 . 7 0 8 2 . 7 0 8

0.151 0.151

No, the function has no defined value for x = 0. x = 0. To verify, suppose x = 0 x = 0 is in the domain of the function f ( x ) = log ( x ) . f ( x ) = log ( x ) . Then there is some number n n such that n = log ( 0 ) . n = log ( 0 ) . Rewriting as an exponential equation gives: 10 n = 0 , 10 n = 0 , which is impossible since no such real number n n exists. Therefore, x = 0 x = 0 is not the domain of the function f ( x ) = log ( x ) . f ( x ) = log ( x ) .

Yes. Suppose there exists a real number x x such that ln x = 2. ln x = 2. Rewriting as an exponential equation gives x = e 2 , x = e 2 , which is a real number. To verify, let x = e 2 . x = e 2 . Then, by definition, ln ( x ) = ln ( e 2 ) = 2. ln ( x ) = ln ( e 2 ) = 2.

No; ln ( 1 ) = 0 , ln ( 1 ) = 0 , so ln ( e 1.725 ) ln ( 1 ) ln ( e 1.725 ) ln ( 1 ) is undefined.

4.4 Section Exercises

Since the functions are inverses, their graphs are mirror images about the line y = x . y = x . So for every point ( a , b ) ( a , b ) on the graph of a logarithmic function, there is a corresponding point ( b , a ) ( b , a ) on the graph of its inverse exponential function.

Shifting the function right or left and reflecting the function about the y-axis will affect its domain.

No. A horizontal asymptote would suggest a limit on the range, and the range of any logarithmic function in general form is all real numbers.

Domain: ( βˆ’ ∞ , 1 2 ) ; ( βˆ’ ∞ , 1 2 ) ; Range: ( βˆ’ ∞ , ∞ ) ( βˆ’ ∞ , ∞ )

Domain: ( βˆ’ 17 4 , ∞ ) ; ( βˆ’ 17 4 , ∞ ) ; Range: ( βˆ’ ∞ , ∞ ) ( βˆ’ ∞ , ∞ )

Domain: ( 5 , ∞ ) ; ( 5 , ∞ ) ; Vertical asymptote: x = 5 x = 5

Domain: ( βˆ’ 1 3 , ∞ ) ; ( βˆ’ 1 3 , ∞ ) ; Vertical asymptote: x = βˆ’ 1 3 x = βˆ’ 1 3

Domain: ( βˆ’ 3 , ∞ ) ; ( βˆ’ 3 , ∞ ) ; Vertical asymptote: x = βˆ’ 3 x = βˆ’ 3

Domain: ( 3 7 , ∞ ) ( 3 7 , ∞ ) ; Vertical asymptote: x = 3 7 x = 3 7 ; End behavior: as x β†’ ( 3 7 ) + , f ( x ) β†’ βˆ’ ∞ x β†’ ( 3 7 ) + , f ( x ) β†’ βˆ’ ∞ and as x β†’ ∞ , f ( x ) β†’ ∞ x β†’ ∞ , f ( x ) β†’ ∞

Domain: ( βˆ’ 3 , ∞ ) ( βˆ’ 3 , ∞ ) ; Vertical asymptote: x = βˆ’ 3 x = βˆ’ 3 ; End behavior: as x β†’ βˆ’ 3 + x β†’ βˆ’ 3 + , f ( x ) β†’ βˆ’ ∞ f ( x ) β†’ βˆ’ ∞ and as x β†’ ∞ x β†’ ∞ , f ( x ) β†’ ∞ f ( x ) β†’ ∞

Domain: ( 1 , ∞ ) ; ( 1 , ∞ ) ; Range: ( βˆ’ ∞ , ∞ ) ; ( βˆ’ ∞ , ∞ ) ; Vertical asymptote: x = 1 ; x = 1 ; x -intercept: ( 5 4 , 0 ) ; ( 5 4 , 0 ) ; y -intercept: DNE

Domain: ( βˆ’ ∞ , 0 ) ; ( βˆ’ ∞ , 0 ) ; Range: ( βˆ’ ∞ , ∞ ) ; ( βˆ’ ∞ , ∞ ) ; Vertical asymptote: x = 0 ; x = 0 ; x -intercept: ( βˆ’ e 2 , 0 ) ; ( βˆ’ e 2 , 0 ) ; y -intercept: DNE

Domain: ( 0 , ∞ ) ; ( 0 , ∞ ) ; Range: ( βˆ’ ∞ , ∞ ) ; ( βˆ’ ∞ , ∞ ) ; Vertical asymptote: x = 0 ; x = 0 ; x -intercept: ( e 3 , 0 ) ; ( e 3 , 0 ) ; y -intercept: DNE

f ( x ) = log 2 ( βˆ’ ( x βˆ’ 1 ) ) f ( x ) = log 2 ( βˆ’ ( x βˆ’ 1 ) )

f ( x ) = 3 log 4 ( x + 2 ) f ( x ) = 3 log 4 ( x + 2 )

x = 2 x = 2

x β‰ˆ 2 .303 x β‰ˆ 2 .303

x β‰ˆ βˆ’ 0.472 x β‰ˆ βˆ’ 0.472

The graphs of f ( x ) = log 1 2 ( x ) f ( x ) = log 1 2 ( x ) and g ( x ) = βˆ’ log 2 ( x ) g ( x ) = βˆ’ log 2 ( x ) appear to be the same; Conjecture: for any positive base b β‰  1 , b β‰  1 , log b ( x ) = βˆ’ log 1 b ( x ) . log b ( x ) = βˆ’ log 1 b ( x ) .

Recall that the argument of a logarithmic function must be positive, so we determine where x + 2 x βˆ’ 4 > 0 x + 2 x βˆ’ 4 > 0 . From the graph of the function f ( x ) = x + 2 x βˆ’ 4 , f ( x ) = x + 2 x βˆ’ 4 , note that the graph lies above the x -axis on the interval ( βˆ’ ∞ , βˆ’ 2 ) ( βˆ’ ∞ , βˆ’ 2 ) and again to the right of the vertical asymptote, that is ( 4 , ∞ ) . ( 4 , ∞ ) . Therefore, the domain is ( βˆ’ ∞ , βˆ’ 2 ) βˆͺ ( 4 , ∞ ) . ( βˆ’ ∞ , βˆ’ 2 ) βˆͺ ( 4 , ∞ ) .

4.5 Section Exercises

Any root expression can be rewritten as an expression with a rational exponent so that the power rule can be applied, making the logarithm easier to calculate. Thus, log b ( x 1 n ) = 1 n log b ( x ) . log b ( x 1 n ) = 1 n log b ( x ) .

log b ( 2 ) + log b ( 7 ) + log b ( x ) + log b ( y ) log b ( 2 ) + log b ( 7 ) + log b ( x ) + log b ( y )

log b ( 13 ) βˆ’ log b ( 17 ) log b ( 13 ) βˆ’ log b ( 17 )

βˆ’ k ln ( 4 ) βˆ’ k ln ( 4 )

ln ( 7 x y ) ln ( 7 x y )

log b ( 4 ) log b ( 4 )

log b ( 7 ) log b ( 7 )

15 log ( x ) + 13 log ( y ) βˆ’ 19 log ( z ) 15 log ( x ) + 13 log ( y ) βˆ’ 19 log ( z )

3 2 log ( x ) βˆ’ 2 log ( y ) 3 2 log ( x ) βˆ’ 2 log ( y )

8 3 log ( x ) + 14 3 log ( y ) 8 3 log ( x ) + 14 3 log ( y )

ln ( 2 x 7 ) ln ( 2 x 7 )

log ( x z 3 y ) log ( x z 3 y )

log 7 ( 15 ) = ln ( 15 ) ln ( 7 ) log 7 ( 15 ) = ln ( 15 ) ln ( 7 )

log 11 ( 5 ) = log 5 ( 5 ) log 5 ( 11 ) = 1 b log 11 ( 5 ) = log 5 ( 5 ) log 5 ( 11 ) = 1 b

log 11 ( 6 11 ) = log 5 ( 6 11 ) log 5 ( 11 ) = log 5 ( 6 ) βˆ’ log 5 ( 11 ) log 5 ( 11 ) = a βˆ’ b b = a b βˆ’ 1 log 11 ( 6 11 ) = log 5 ( 6 11 ) log 5 ( 11 ) = log 5 ( 6 ) βˆ’ log 5 ( 11 ) log 5 ( 11 ) = a βˆ’ b b = a b βˆ’ 1

2.81359 2.81359

0.93913 0.93913

βˆ’ 2.23266 βˆ’ 2.23266

x = 4 ; x = 4 ; By the quotient rule: log 6 ( x + 2 ) βˆ’ log 6 ( x βˆ’ 3 ) = log 6 ( x + 2 x βˆ’ 3 ) = 1. log 6 ( x + 2 ) βˆ’ log 6 ( x βˆ’ 3 ) = log 6 ( x + 2 x βˆ’ 3 ) = 1.

Rewriting as an exponential equation and solving for x : x :

6 1 = x + 2 x βˆ’ 3 0 = x + 2 x βˆ’ 3 βˆ’ 6 0 = x + 2 x βˆ’ 3 βˆ’ 6 ( x βˆ’ 3 ) ( x βˆ’ 3 ) 0 = x + 2 βˆ’ 6 x + 18 x βˆ’ 3 0 = x βˆ’ 4 x βˆ’ 3 ​ x = 4 6 1 = x + 2 x βˆ’ 3 0 = x + 2 x βˆ’ 3 βˆ’ 6 0 = x + 2 x βˆ’ 3 βˆ’ 6 ( x βˆ’ 3 ) ( x βˆ’ 3 ) 0 = x + 2 βˆ’ 6 x + 18 x βˆ’ 3 0 = x βˆ’ 4 x βˆ’ 3 ​ x = 4

Checking, we find that log 6 ( 4 + 2 ) βˆ’ log 6 ( 4 βˆ’ 3 ) = log 6 ( 6 ) βˆ’ log 6 ( 1 ) log 6 ( 4 + 2 ) βˆ’ log 6 ( 4 βˆ’ 3 ) = log 6 ( 6 ) βˆ’ log 6 ( 1 ) is defined, so x = 4. x = 4.

Let b b and n n be positive integers greater than 1. 1. Then, by the change-of-base formula, log b ( n ) = log n ( n ) log n ( b ) = 1 log n ( b ) . log b ( n ) = log n ( n ) log n ( b ) = 1 log n ( b ) .

4.6 Section Exercises

Determine first if the equation can be rewritten so that each side uses the same base. If so, the exponents can be set equal to each other. If the equation cannot be rewritten so that each side uses the same base, then apply the logarithm to each side and use properties of logarithms to solve.

The one-to-one property can be used if both sides of the equation can be rewritten as a single logarithm with the same base. If so, the arguments can be set equal to each other, and the resulting equation can be solved algebraically. The one-to-one property cannot be used when each side of the equation cannot be rewritten as a single logarithm with the same base.

x = βˆ’ 1 3 x = βˆ’ 1 3

n = βˆ’ 1 n = βˆ’ 1

b = 6 5 b = 6 5

x = 10 x = 10

No solution

p = log ( 17 8 ) βˆ’ 7 p = log ( 17 8 ) βˆ’ 7

k = βˆ’ ln ( 38 ) 3 k = βˆ’ ln ( 38 ) 3

x = ln ( 38 3 ) βˆ’ 8 9 x = ln ( 38 3 ) βˆ’ 8 9

x = ln 12 x = ln 12

x = ln ( 3 5 ) βˆ’ 3 8 x = ln ( 3 5 ) βˆ’ 3 8

no solution

x = ln ( 3 ) x = ln ( 3 )

10 βˆ’ 2 = 1 100 10 βˆ’ 2 = 1 100

n = 49 n = 49

k = 1 36 k = 1 36

x = 9 βˆ’ e 8 x = 9 βˆ’ e 8

n = 1 n = 1

x = Β± 10 3 x = Β± 10 3

x = 0 x = 0

x = 3 4 x = 3 4

x = 9 x = 9

x = e 2 3 β‰ˆ 2.5 x = e 2 3 β‰ˆ 2.5

x = βˆ’ 5 x = βˆ’ 5

x = e + 10 4 β‰ˆ 3.2 x = e + 10 4 β‰ˆ 3.2

x = 11 5 β‰ˆ 2.2 x = 11 5 β‰ˆ 2.2

x = 101 11 β‰ˆ 9.2 x = 101 11 β‰ˆ 9.2

about $ 27 , 710.24 $ 27 , 710.24

about 5 years

ln ( 17 ) 5 β‰ˆ 0.567 ln ( 17 ) 5 β‰ˆ 0.567

x = log ( 38 ) + 5 log ( 3 )    4 log ( 3 ) β‰ˆ 2.078 x = log ( 38 ) + 5 log ( 3 )    4 log ( 3 ) β‰ˆ 2.078

x β‰ˆ 2.2401 x β‰ˆ 2.2401

x β‰ˆ βˆ’ 44655 . 7143 x β‰ˆ βˆ’ 44655 . 7143

about 5.83 5.83

t = ln ( ( y A ) 1 k ) t = ln ( ( y A ) 1 k )

t = ln ( ( T βˆ’ T s T 0 βˆ’ T s ) βˆ’ 1 k ) t = ln ( ( T βˆ’ T s T 0 βˆ’ T s ) βˆ’ 1 k )

4.7 Section Exercises

Half-life is a measure of decay and is thus associated with exponential decay models. The half-life of a substance or quantity is the amount of time it takes for half of the initial amount of that substance or quantity to decay.

Doubling time is a measure of growth and is thus associated with exponential growth models. The doubling time of a substance or quantity is the amount of time it takes for the initial amount of that substance or quantity to double in size.

An order of magnitude is the nearest power of ten by which a quantity exponentially grows. It is also an approximate position on a logarithmic scale; Sample response: Orders of magnitude are useful when making comparisons between numbers that differ by a great amount. For example, the mass of Saturn is 95 times greater than the mass of Earth. This is the same as saying that the mass of Saturn is about 10 2 10 2 times, or 2 orders of magnitude greater, than the mass of Earth.

f ( 0 ) β‰ˆ 16.7 ; f ( 0 ) β‰ˆ 16.7 ; The amount initially present is about 16.7 units.

exponential; f ( x ) = 1.2 x f ( x ) = 1.2 x

logarithmic

about 1.4 1.4 years

about 7.3 7.3 years

4 4 half-lives; 8.18 8.18 minutes

M = 2 3 log ( S S 0 ) log ( S S 0 ) = 3 2 M S S 0 = 10 3 M 2 S = S 0 10 3 M 2 M = 2 3 log ( S S 0 ) log ( S S 0 ) = 3 2 M S S 0 = 10 3 M 2 S = S 0 10 3 M 2

Let y = b x y = b x for some non-negative real number b b such that b β‰  1. b β‰  1. Then,

ln ( y ) = ln ( b x ) ln ( y ) = x ln ( b ) e ln ( y ) = e x ln ( b )             y = e x ln ( b ) ln ( y ) = ln ( b x ) ln ( y ) = x ln ( b ) e ln ( y ) = e x ln ( b )             y = e x ln ( b )

A = 125 e ( βˆ’ 0.3567 t ) ; A β‰ˆ 43 A = 125 e ( βˆ’ 0.3567 t ) ; A β‰ˆ 43 mg

about 60 60 days

A ( t ) = 250 e ( βˆ’ 0.00822 t ) ; A ( t ) = 250 e ( βˆ’ 0.00822 t ) ; half-life: about 84 84 minutes

r β‰ˆ βˆ’ 0.0667 , r β‰ˆ βˆ’ 0.0667 , So the hourly decay rate is about 6.67 % 6.67 %

f ( t ) = 1350 e ( 0.03466 t ) ; f ( t ) = 1350 e ( 0.03466 t ) ; after 3 hours: P ( 180 ) β‰ˆ 691 , 200 P ( 180 ) β‰ˆ 691 , 200

f ( t ) = 256 e ( 0.068110 t ) ; f ( t ) = 256 e ( 0.068110 t ) ; doubling time: about 10 10 minutes

about 88 88 minutes

T ( t ) = 90 e ( βˆ’ 0.008377 t ) + 75 , T ( t ) = 90 e ( βˆ’ 0.008377 t ) + 75 , where t t is in minutes.

about 113 113 minutes

log ( x ) = 1.5 ; x β‰ˆ 31.623 log ( x ) = 1.5 ; x β‰ˆ 31.623

MMS magnitude: 5.82 5.82

N ( 3 ) β‰ˆ 71 N ( 3 ) β‰ˆ 71

4.8 Section Exercises

Logistic models are best used for situations that have limited values. For example, populations cannot grow indefinitely since resources such as food, water, and space are limited, so a logistic model best describes populations.

Regression analysis is the process of finding an equation that best fits a given set of data points. To perform a regression analysis on a graphing utility, first list the given points using the STAT then EDIT menu. Next graph the scatter plot using the STAT PLOT feature. The shape of the data points on the scatter graph can help determine which regression feature to use. Once this is determined, select the appropriate regression analysis command from the STAT then CALC menu.

The y -intercept on the graph of a logistic equation corresponds to the initial population for the population model.

P ( 0 ) = 22 P ( 0 ) = 22 ; 175

p β‰ˆ 2.67 p β‰ˆ 2.67

y -intercept: ( 0 , 15 ) ( 0 , 15 )

about 6.8 6.8 months.

About 38 wolves

About 8.7 years

f ( x ) = 776.682 ( 1.426 ) x f ( x ) = 776.682 ( 1.426 ) x

f ( x ) = 731.92 e -0.3038 x f ( x ) = 731.92 e -0.3038 x

When f ( x ) = 250 , x β‰ˆ 3.6 f ( x ) = 250 , x β‰ˆ 3.6

y = 5.063 + 1.934 log ( x ) y = 5.063 + 1.934 log ( x )

When f ( 10 ) β‰ˆ 2.3 f ( 10 ) β‰ˆ 2.3

When f ( x ) = 8 , x β‰ˆ 0.82 f ( x ) = 8 , x β‰ˆ 0.82

f ( x ) = 25.081 1 + 3.182 e βˆ’ 0.545 x f ( x ) = 25.081 1 + 3.182 e βˆ’ 0.545 x

When f ( x ) = 68 , x β‰ˆ 4.9 f ( x ) = 68 , x β‰ˆ 4.9

f ( x ) = 1.034341 ( 1.281204 ) x f ( x ) = 1.034341 ( 1.281204 ) x ; g ( x ) = 4.035510 g ( x ) = 4.035510 ; the regression curves are symmetrical about y = x y = x , so it appears that they are inverse functions.

f βˆ’ 1 ( x ) = ln ( a ) - ln ( c x - 1 ) b f βˆ’ 1 ( x ) = ln ( a ) - ln ( c x - 1 ) b

Review Exercises

exponential decay; The growth factor, 0.825 , 0.825 , is between 0 0 and 1. 1.

y = 0.25 ( 3 ) x y = 0.25 ( 3 ) x

$ 42 , 888.18 $ 42 , 888.18

continuous decay; the growth rate is negative.

domain: all real numbers; range: all real numbers strictly greater than zero; y -intercept: (0, 3.5);

g ( x ) = 7 ( 6.5 ) βˆ’ x ; g ( x ) = 7 ( 6.5 ) βˆ’ x ; y -intercept: ( 0 , 7 ) ; ( 0 , 7 ) ; Domain: all real numbers; Range: all real numbers greater than 0. 0.

17 x = 4913 17 x = 4913

log a b = βˆ’ 2 5 log a b = βˆ’ 2 5

x = 64 1 3 = 4 x = 64 1 3 = 4

log ( 0 .000001 ) = βˆ’ 6 log ( 0 .000001 ) = βˆ’ 6

ln ( e βˆ’ 0.8648 ) = βˆ’ 0.8648 ln ( e βˆ’ 0.8648 ) = βˆ’ 0.8648

Domain: x > βˆ’ 5 ; x > βˆ’ 5 ; Vertical asymptote: x = βˆ’ 5 ; x = βˆ’ 5 ; End behavior: as x β†’ βˆ’ 5 + , f ( x ) β†’ βˆ’ ∞ x β†’ βˆ’ 5 + , f ( x ) β†’ βˆ’ ∞ and as x β†’ ∞ , f ( x ) β†’ ∞ . x β†’ ∞ , f ( x ) β†’ ∞ .

log 8 ( 65 x y ) log 8 ( 65 x y )

ln ( z x y ) ln ( z x y )

log y ( 12 ) log y ( 12 )

ln ( 2 ) + ln ( b ) + ln ( b + 1 ) βˆ’ ln ( b βˆ’ 1 ) 2 ln ( 2 ) + ln ( b ) + ln ( b + 1 ) βˆ’ ln ( b βˆ’ 1 ) 2

log 7 ( v 3 w 6 u 3 ) log 7 ( v 3 w 6 u 3 )

x = log ( 125 ) log ( 5 ) + 17 12 = 5 3 x = log ( 125 ) log ( 5 ) + 17 12 = 5 3

x = βˆ’ 3 x = βˆ’ 3

x = ln ( 11 ) x = ln ( 11 )

a = e 4 βˆ’ 3 a = e 4 βˆ’ 3

x = Β± 9 5 x = Β± 9 5

about 5.45 5.45 years

f βˆ’ 1 ( x ) = 2 4 x βˆ’ 1 3 f βˆ’ 1 ( x ) = 2 4 x βˆ’ 1 3

f ( t ) = 300 ( 0.83 ) t ; f ( t ) = 300 ( 0.83 ) t ; f ( 24 ) β‰ˆ 3.43 β€Š β€Š g f ( 24 ) β‰ˆ 3.43 β€Š β€Š g

about 45 45 minutes

about 8.5 8.5 days

exponential

y = 4 ( 0.2 ) x ; y = 4 ( 0.2 ) x ; y = 4 e -1.609438 x y = 4 e -1.609438 x

about 7.2 7.2 days

logarithmic; y = 16.68718 βˆ’ 9.71860 ln ( x ) y = 16.68718 βˆ’ 9.71860 ln ( x )

Practice Test

About 13 dolphins.

$ 1,947 $ 1,947

y -intercept: ( 0 , 5 ) ( 0 , 5 )

8.5 a = 614.125 8.5 a = 614.125

x = ( 1 7 ) 2 = 1 49 x = ( 1 7 ) 2 = 1 49

ln ( 0.716 ) β‰ˆ βˆ’ 0.334 ln ( 0.716 ) β‰ˆ βˆ’ 0.334

Domain: x < 3 ; x < 3 ; Vertical asymptote: x = 3 ; x = 3 ; End behavior: x β†’ 3 βˆ’ , f ( x ) β†’ βˆ’ ∞ x β†’ 3 βˆ’ , f ( x ) β†’ βˆ’ ∞ and x β†’ βˆ’ ∞ , f ( x ) β†’ ∞ x β†’ βˆ’ ∞ , f ( x ) β†’ ∞

log t ( 12 ) log t ( 12 )

3 ln ( y ) + 2 ln ( z ) + ln ( x βˆ’ 4 ) 3 3 ln ( y ) + 2 ln ( z ) + ln ( x βˆ’ 4 ) 3

x = ln ( 1000 ) ln ( 16 ) + 5 3 β‰ˆ 2.497 x = ln ( 1000 ) ln ( 16 ) + 5 3 β‰ˆ 2.497

a = ln ( 4 ) + 8 10 a = ln ( 4 ) + 8 10

x = ln ( 9 ) x = ln ( 9 )

x = Β± 3 3 2 x = Β± 3 3 2

f ( t ) = 112 e βˆ’ .019792 t ; f ( t ) = 112 e βˆ’ .019792 t ; half-life: about 35 35 days

T ( t ) = 36 e βˆ’ 0.025131 t + 35 ; T ( 60 ) β‰ˆ 43 o F T ( t ) = 36 e βˆ’ 0.025131 t + 35 ; T ( 60 ) β‰ˆ 43 o F

exponential; y = 15.10062 ( 1.24621 ) x y = 15.10062 ( 1.24621 ) x

logistic; y = 18.41659 1 + 7.54644 e βˆ’ 0.68375 x y = 18.41659 1 + 7.54644 e βˆ’ 0.68375 x

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Chapter 4: Structuring, Paragraphing, and Styling

4.2 Body Paragraphs: An Overview

Amanda Lloyd

Body Paragraph Development

The term body paragraph refers to any paragraph that appears between the introductory and concluding sections of an essay. A good body paragraph should support the claim made in the thesis statement by developing only one key supporting idea. This idea is often referred to as a sub-claim.

Some sub-claims will take more time to develop than others, so body paragraph length can and often should vary in order to maintain your reader’s interest. When constructing a body paragraph, the most important objectives are to stay on-topic and to fully develop your sub-claim.

When constructing a body paragraph, make sure that you never begin or end with a quotation or a paraphrase. Rather, you should think of a body paragraph as conforming to the following pattern.

Typically, a body paragraph contains three main elements:

  • a topic sentence ,
  • supporting evidence, and
  • an explanation of that evidence.

While body paragraphs in some essay assignments (certain summary assignments for example) may not adhere to this pattern exactly, for the most part, following this basic formula will help you to construct a focused and complete body paragraph.

See section 4.3 for information on topic sentences, section 4.4 for information on supporting evidence, and section 4.5 for information on explaining the evidence.

4.2 Body Paragraphs: An Overview by Amanda Lloyd is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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4.2: Writing Assignments

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  • Page ID 133159

  • Lyle Cleeland & Lisa Moody
  • James Cook University via James Cook University

Hands on laptop

Introduction

Assignments are a common method of assessment at university and require careful planning and good quality research. Developing critical thinking and writing skills are also necessary to demonstrate your ability to understand and apply information about your topic. It is not uncommon to be unsure about the processes of writing assignments at university.

This chapter has a collection of resources that will provide you with the skills and strategies to understand assignment requirements and effectively plan, research, write, and edit your assignments.

Task Analysis and Deconstructing an Assignment

It is important that you spend sufficient time understanding all the requirements before you begin researching and writing your assignments.

The assessment task description (located in your subject outline) provides key information about an assessment item, including the question. It is essential to scan this document for topic, task, and limiting words. If there are any elements you do not understand, you should clarify these as early as possible.

Make sure you have a clear understanding of what the task word requires you to address.

The marking criteria or rubric , is an important document to look at before you begin your assignment. This outlines how your assignment will be marked and should be used as a checklist to make sure you have included all the information required.

The assessment task description will also include the:

  • Word limit (or word count)
  • Referencing style and research expectations
  • Formatting requirements

For a more detailed discussion on task analysis, criteria sheets, and marking rubrics, visit the chapter Managing Assessments.

Preparing your ideas

Concept map on whiteboard

Brainstorm or concept map: List possible ideas to address each part of the assignment task based on what you already know about the topic from lectures and weekly readings.

Finding appropriate information: Learn how to find scholarly information for your assignments which is:

See the chapter Working With Information for a more detailed explanation .

What is Academic Writing?

Academic writing tone and style.

Many of the assessment items you prepare will require an academic writing style. Sometimes this feels awkward when you begin. However, it is good to know that practice at academic writing reduces this feeling.

Thesis statements

One of the most important steps in writing an essay is constructing your working thesis statement. A thesis statement tells the reader the purpose, argument, or direction you will take to answer your assignment question. It is found in the introduction paragraph. The thesis statement:

  • Directly relates to the task . Your thesis statement may even contain some of the key words or synonyms from the task description.
  • Does more than restate the question.
  • Is specific and uses precise language.
  • Lets your reader know your position or the main argument that you will support with evidence throughout your assignment.
  • The subject is the key content area you will be covering.
  • The premise is the key argument or position.

A key element of your thesis statement should be included in the topic sentence of each paragraph.

Planning your assignment structure

Image of the numbers 231

When planning and drafting assignments, it is important to consider the structure of your writing. Academic writing should have a clear and logical structure and incorporate academic research to support your ideas. It can be hard to get started and at first you may feel nervous about the size of the task. This is normal. If you break your assignment into smaller pieces, it will seem more manageable as you can approach the task in sections. Refer to your brainstorm or plan. These ideas should guide your research and will also inform what you write in your draft. It is sometimes easier to draft your assignment using the 2-3-1 approach, that is, write the body paragraphs first followed by the conclusion and finally the introduction.

No one’s writing is the best quality on the first few drafts, not even professional writers. It is strongly advised that you accept that your first few drafts will feel rough. Ultimately, it is the editing and review processes which lead to good quality ideas and writing.

Writing introductions and conclusions

Clear and purposeful introductions and conclusions in assignments are fundamental to effective academic writing. Your introduction should tell the reader what is going to be covered and how you intend to approach this. Your conclusion should summarise your argument or discussion and signal to the reader that you have come to a conclusion with a final statement.

Writing introductions

An effective introduction needs to inform your reader by establishing what the paper is about and provide four basic elements:

  • A brief background or overview of your assignment topic and key information that reader needs to understand your thesis statement.
  • Scope of discussion (key points discussed in body paragraphs).
  • A thesis statement (see section above).

The below example demonstrates the different elements of an introductory paragraph.

1) Information technology is having significant effects on the communication of individuals and organisations in different professions. 2) Digital technology is now widely utilised in health settings, by health professionals. Within the public health field, doctors and nurses need to engage with ongoing professional development relating to digital technology in order to ensure efficient delivery of services to patients and communities. 3) Clearly, information technology has significant potential to improve health care and medical education, but some health professionals are reluctant to use it.

1 Brief background/overview | 2 Scope of what will be covered | 3 The thesis statement

Writing conclusions

You should aim to end your assignments with a strong conclusion. Your conclusion should restate your thesis statement and summarise the key points you have used to prove this thesis. Finish with a key point as a final impactful statement. If your assessment task asks you to make recommendations, you may need to allocate more words to the conclusion or add a separate recommendations section before the conclusion. Use the checklist below to check your conclusion is doing the right job.

Conclusion checklist

  • Have you referred to the assignment question and restated your argument (or thesis statement), as outlined in the introduction?
  • Have you pulled together all the threads of your essay into a logical ending and given it a sense of unity?
  • Have you presented implications or recommendations in your conclusion? (if required by your task).
  • Have you added to the overall quality and impact of your essay? This is your final statement about this topic; thus, a key take-away point can make a great impact on the reader.
  • Do not add any new material or direct quotes in your conclusion.

This below example demonstrates the different elements of a concluding paragraph.

1) Clearly, communication of individuals and organisations is substantially influenced or affected by information technology across professions. 2) Managers must ensure that effective in-house training programs are provided for public health professionals, so that they become more familiar with the particular digital technologies 3) In addition, the patients and communities being served by public health professionals benefit when communication technologies are effectively implemented. 4) The Australian health system may never be completely free of communication problems, however, ensuring appropriate and timely professional development, provision of resource sand infrastructure will enhance service provision and health outcomes.

1 Reference to thesis statement – In this essay the writer has taken the position that training is required for both employees and employers . | 2-3 Structure overview – Here the writer pulls together the main ideas in the essay. | 4 Final summary statement that is based on the evidence.

Note: The examples in this document are adapted from the University of Canberra and used under a CC-BY-SA-3.0 licence.

Writing paragraphs

Each paragraph should have its own clearly identified Topic Sentence or main idea which relates to the argument or point (thesis) you are developing. This idea should then be explained by additional sentences which you have paraphrased from good quality sources and referenced according to the recommended guidelines of your subject (see the chapter Working with Information ). Paragraphs are characterised by moving from general information to the specific details. A common structure for paragraphs in academic writing is as follows.

Topic Sentence

The first sentence of the paragraph is the Topic Sentence. This is the main idea of the paragraph and tells the reader what you will discuss in more detail below. Each Topic Sentence should address one aspect of your overall argument.

Supporting Sentences

Supporting Sentences provide more explanation, evidence, data, analogies, and/or analysis of the main idea.

Linking/Concluding Sentence

Some paragraphs are best linked to the following paragraph through a Linking/Concluding Sentence. Not every paragraph lends itself to this type of sentence.

Use the checklist below to check your paragraphs are clear and well formed.

Paragraph checklist

  • Does your paragraph have a clear main idea?
  • Is everything in the paragraph related to this main idea?
  • Is the main idea adequately developed and explained?
  • Have you included evidence to support your ideas?
  • Have you concluded the paragraph by connecting it to your overall topic (where appropriate)?

Writing sentences

Make sure all the sentences in your paragraphs make sense. Each sentence must contain a verb to be a complete sentence. Avoid incomplete sentences or ideas that are unfinished and create confusion for your reader. Also avoid overly long sentences, which happens when you join two ideas or clauses without using the appropriate punctuation. Address only one key idea per sentence. See the chapter English Language Foundations for examples and further explanation.

Use transitions (linking words and phrases) to connect your ideas between paragraphs and make your writing flow. The order that you structure the ideas in your assignment should reflect the structure you have outlined in your introduction. Refer to the transition words table in the chapter English Language Foundations.

Paraphrasing and Synthesising

What is paraphrasing.

Paraphrasing is changing the writing of another author into your words while retaining the original meaning. You must acknowledge the original author as the source of the information in your citation. Follow the steps in this table to help you build your skills in paraphrasing. Note: paraphrasing generally means that the rewritten section is the same or a similar length to the original.

Example of paraphrasing

Please note that these examples and in-text citations are for instructional purposes only.

Original text

Health care professionals assist people, often when they are at their most vulnerable . To provide the best care and understand their needs, workers must demonstrate good communication skills . They must develop patient trust and provide empathy to effectively work with patients who are experiencing a variety of situations including those who may be suffering from trauma or violence, physical or mental illness or substance abuse (French & Saunders, 2018).

Poor quality paraphrase example

This is a poor example of paraphrasing. Some synonyms have been used and the order of a few words changed within the sentences. However, the colours of the sentences indicate that the paragraph follows the same structure as the original text.

Health care sector workers are often responsible for vulnerable patients. To understand patients and deliver good service , they need to be excellent communicators . They must establish patient rapport and show empathy if they are to successfully care for patients from a variety of backgrounds and with different medical, psychological and social needs (French & Saunders, 2018).

A good quality paraphrase example

This example demonstrates a better quality paraphrase. The author has demonstrated more understanding of the overall concept in the text by using the keywords as the basis to reconstruct the paragraph.

Empathetic communication is a vital skill for health care workers. Professionals in these fields are often responsible for patients with complex medical, psychological and social needs. Empathetic communication assists in building rapport and gaining the necessary trust to assist these vulnerable patients by providing appropriate supportive care (French & Saunders, 2018).

The good quality paraphrase example demonstrates understanding of the overall concept in the text by using key words as the basis to reconstruct the paragraph. Note how the blocks of colour have been broken up to see how much the structure has changed from the original text.

What is synthesising?

Synthesising means to bring together more than one source of information to strengthen your argument. Once you have learnt how to paraphrase the ideas of one source at a time, you can consider adding additional sources to support your argument. Synthesis demonstrates your understanding and ability to show connections between multiple pieces of evidence to support your ideas and is a more advanced academic thinking and writing skill.

Follow the steps in this table to improve your synthesis techniques.

Example of synthesis

There is a relationship between academic procrastination and mental health outcomes. Procrastination has been found to have a negative effect on students’ well-being (Balkis, & Duru, 2016). Yerdelen et al.’s (2016) research results suggest that there is a positive association between procrastination and anxiety. This is corroborated by Custer’s (2018) findings which indicate that students with higher levels of procrastination also report greater levels of anxiety. Therefore, it could be argued that procrastination is an ineffective learning strategy that leads to increased levels of distress.

Topic sentence | Statements using paraphrased evidence | Critical thinking (student voice) | Concluding statement – linking to topic sentence

This example demonstrates a simple synthesis. The author has developed a paragraph with one central theme and included explanatory sentences complete with in-text citations from multiple sources. Note how the blocks of colour have been used to illustrate the paragraph structure and synthesis (i.e. statements using paraphrased evidence from several sources). A more complex synthesis may include more than one citation per sentence.

Paraphrasing and synthesising are powerful tools that you can use to support the main idea of a paragraph. It is likely that you will regularly use these skills at university to incorporate evidence into explanatory sentences and strengthen your essay. It is important to paraphrase and synthesise because:

  • Paraphrasing is regarded more highly at university than direct quoting.
  • Paraphrasing can also help you better understand the material.
  • Paraphrasing and synthesising demonstrate that you have understood what you have read through your ability to summarise and combine arguments from the literature using your own words.

Creating an Argument

What does this mean.

In academic writing, if you are asked to create an argument, this means you are asked to have a position on a particular topic, and then justify your position using evidence from valid scholarly sources.

What skills do you need to create an argument?

In order to create a good and effective argument, you need to be able to:

  • Read critically to find evidence.
  • Plan your argument.
  • Think and write critically throughout your paper to enhance your argument.

For tips on how to read and write critically, refer to the chapter Thinking for more information. A formula for developing a strong argument is presented below.

A formula for a good argument

A diagram on the formula for a ggood argument which includes deciding what side of argument you are on, research evidence to support your argument, create a plan to create a logically flowing argument and writing your argument

What does an argument look like?

As can be seen from the figure above, including evidence is a key element of a good argument. While this may seem like a straightforward task, it can be difficult to think of wording to express your argument. The table below provides examples of how you can illustrate your argument in academic writing.

Editing and proofreading (reviewing)

Once you have finished writing your first draft it is recommended that you spend time revising your work. Proofreading and editing are two different stages of the revision process.

  • Editing considers the overall focus or bigger picture of the assignment.
  • Proofreading considers the finer details.

Editing mindmap with the words sources, content,s tructure and style. Proofreading mindmap with the words referencing, word choice, grammar and spelling and punctuation

As can be seen in the figure above, there are four main areas that you should review during the editing phase of the revision process. The main things to consider when editing include content, structure, style, and sources. It is important to check that all the content relates to the assignment task, the structure is appropriate for the purposes of the assignment, the writing is academic in style, and that sources have been adequately acknowledged. Use the checklist below when editing your work.

Editing checklist

  • Have I answered the question accurately?
  • Do I have enough credible, scholarly supporting evidence?
  • Is my writing tone objective and formal enough or have I used emotive and informal language?
  • Have I written in third person, not first person?
  • Do I have appropriate in-text citations for all my information?
  • Have I included the full details for all my in-text citations in my reference list?

During proofreading, it is important to check your work for word choice, grammar and spelling, punctuation, and referencing errors. It can be easy to mis-type words like ‘from’ and ‘form’ or mix up words like ‘trail’ and ‘trial’ when writing about research, apply American rather than Australian spelling, include unnecessary commas, or incorrectly format your references list. The checklist below is a useful guide that you can use when proofreading your work.

Proofreading checklist

  • Is my spelling and grammar accurate?
  • Are they complete?
  • Do they all make sense?
  • Do the different elements (subject, verb, nouns, pronouns) within my sentences agree?
  • Are my sentences too long and complicated?
  • Do they contain only one idea per sentence?
  • Is my writing concise? Take out words that do not add meaning to your sentences.
  • Have I used appropriate discipline specific language but avoided words I don’t know or understand that could possibly be out of context?
  • Have I avoided discriminatory language and colloquial expressions (slang)?
  • Is my referencing formatted correctly according to my assignment guidelines? (For more information on referencing, refer to the Managing Assessment feedback section).

This chapter has examined the experience of writing assignments. It began by focusing on how to read and break down an assignment question, then highlighted the key components of essays. Next, it examined some techniques for paraphrasing and summarising, and how to build an argument. It concluded with a discussion on planning and structuring your assignment and giving it that essential polish with editing and proofreading. Combining these skills and practising them can greatly improve your success with this very common form of assessment.

  • Academic writing requires clear and logical structure, critical thinking and the use of credible scholarly sources.
  • A thesis statement is important as it tells the reader the position or argument you have adopted in your assignment.
  • Spending time analysing your task and planning your structure before you start to write your assignment is time well spent.
  • Information you use in your assignment should come from credible scholarly sources such as textbooks and peer reviewed journals. This information needs to be paraphrased and referenced appropriately.
  • Paraphrasing means putting something into your own words and synthesising means to bring together several ideas from sources.
  • Creating an argument is a four step process and can be applied to all types of academic writing.
  • Editing and proofreading are two separate processes.

Balkis, M., & Duru, E. (2016). Procrastination, self-regulation failure, academic life satisfaction, and affective well-being: underregulation or misregulation form. European Journal of Psychology of Education, 31 (3), 439-459.

Custer, N. (2018). Test anxiety and academic procrastination among prelicensure nursing students. Nursing Education Perspectives, 39 (3), 162-163.

Yerdelen, S., McCaffrey, A., & Klassen, R. M. (2016). Longitudinal examination of procrastination and anxiety, and their relation to self-efficacy for self-regulated learning: Latent growth curve modeling. Educational Sciences: Theory & Practice, 16 (1), 5-22.

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